1. Field of the Invention
The present invention relates to an optical disk on which a visible image can be formed by laser light applied from an optical pickup.
2. Description of the Related Art
Optical disk reproducing devices that read a signal recorded on a disk using an optical pickup are widely available, and, recently, optical disk recording and reproducing devices configured to include, in addition to the reproducing capability, the capability of recording a signal on a disk by laser light applied from an optical pickup have been introduced to the market.
When such an optical disk recording and reproducing device is used to record a signal on a disk, in order to identify the content of the signal recorded on the disk, it is necessary to read the signal recorded on the disk. To avoid such necessity, after completion of a signal recording operation, some users place, on a surface opposite to a recording surface of the disk, a label or the like having information of the recorded content printed thereon, for example, song titles, when music is recorded, while other users write song titles or the like on the non-recording surface using a felt-tipped pen or the like.
However, such methods including a step of placing a label or the like or of writing song titles or the like are inconvenient and can adversely affect the reproducing operation of the signal recorded on the disk. As a method to overcome such a problem, a technique for forming a visible image on a photosensitive surface of an optical disk by laser light has been developed.
Also, a technique that enables a visible image to be formed in multiple colors has been developed.
However, currently known techniques remain problematic in that, because a visible image is to be formed on a signal surface on which a data signal is recorded, when the recording capacity for data signals is large, the area for forming a visible image is reduced and it is usually impossible to display information sufficient to identify all recorded data. On the other hand, when the formation of a visible image on an optical disk is performed on a surface opposite to the signal recording surface of the disk, there is another problem in that users must inconveniently turn the disk upside down after completion of a recording operation of data onto the disk.